Overheating protection arrangement in an electric sauna unit

ABSTRACT

In an electric sauna unit having an air passage which is open at bottom and top through which air flows during normal operation and in which electric heating elements are located there is provided an opening in the wall of the passage in the upper portion of the air passage. During normal operation cool air flows through the opening from the outside to the inside of the air passage, but if the air passage is obstructed the flow of heated air will leave the air passage through said opening. A sensing element operatively connected to a thermostatic switch controlling the supply circuit of the heating elements is located to sense the temperature of air passing through the opening and to actuate the thermostatic switch at a predetermined temperature in order to interrupt the supply circuit.

[ 0st. elf: 1.973

[ OVERHEATING PROTECTION 3,452,369 7/1969 Jones et al 219/366 x ARRANGEMENT EN AN ELECTRIC SAUNA 3,277,274 10/1966 Raabe 219/367 X UNIT FOREIGN PATENTS 0R APPLICATIONS [76] Inventor: Sven 010i Jansen, Fredagsgrand 13, 416,870 1/1967 Switzerland 219/370 Halmsted, Sweden Prima Examiner-A. Bartis 22 Fld: F .7197: 1 l e eh AttorneyLadas, Parry, Von Gehr, Goldsmith & [21] Appl. No.: 223,926 Deschamps [30] Foreign Application Priority Data [57] ABSTRACT Feb. 8, 1971 Sweden 1531/71 In an electric sauna unit having an air passage which is i open at bottom and top through which air flows dur- [52] ELS- C! 219/363, 4/160, 219/342, ing normal operation and in which electric heating eh 219/364, 219/367 ements are located there is provided an opening in the [51] Int. Cl H0511 1/02, F24h 3/00 n f the passage in the upper portion f the i [58] Field of Search 219/363, 364, 365-371, Sage During nonha] operation cool fl through 219574-376 342; 160464 theopening from the outside to the inside of the air passage, but if the air passage is obstructed the flow of [561 References cued heated air will leave the air passage through said open- UNITED STATES PATENTS ing. A sensing element operatively connected to a 3,348,021 10/1967 Skogland et al. 219/364 x thermostatic Switch controlling the pp y circuit of 2,512,892 6/1950 Forsberg 219/374 X the heating elements is located to sense the tempera- 3.305.665 1967 Laing 219L370 ture of air passing through the opening and to actuate 3,341,675 1967 2l9/364 UX the thermostatic switch at a predetermined tempera- 3'400248 9/1968 Isomaa 219/365 X ture in order to interrupt the supply circuit. 2,988,626 6/1961 Buttner -219/364 X 3,147,367 9/1964 Magnusson 219/365 4 Claims, 2 Drawing Figures NORMAL UNOBSTRUCTED 4 1 1 ,OBSTRUCTION AIR FLOW I 1 SENSING, J E T f LEMEN I I I l 1 1 I 12 17c" l I J l 1 f TH ERMOSTATIC SWITCH @VERHEATKNG PRUTEQTHQN ARRANGEMENT EN AN ELE J'llllllll'J SAUNA UNlT The invention relates to an electric sauna unit comprising a casing which forms an air passage open at the bottom and at the top and is adapted to be mounted adjacent a wall of the sauna space, and further comprising electric heating elements located in the air passage.

it happens that a sauna unit of this type by carelessness or mistake is covered by an object preventing the air circulation through the air passage, which results in overheating of the unit and ignition of the sauna wall behind, which is usually faced by a wood panel, as well as the covering object if it is combustible. Although the fires initiated in this manner are not very common the mere fact. that there is a risk for fire in connection with these electric sauna units, at least the present embodiments thereof, is a sufficient reason for endeavouring to arrange the sauna unit in such a manner that the risk will be completely eliminated.

The primary object of this invention is to provide an electric sauna unit of the kind referred to, which eliminates the risk for fires of the related type.

According to the invention there is provided an electric sauna unit comprising a casing forming the wall of an air passage open at the bottom and at the top, said casing being adapted to be mounted adjacent a wall in a sauna space, at least one electric heating element located in the air passage, a thermostatic switch for controlling the current supply to the heating element, an opening formed by the wall of the air passage in an upper part thereof, and a sensing element operatively connected with the thermostatic switch and sensing the temperature of air flow passing through the opening when the sauna unit is operated, to actuate the thermostatic switch at a predetermined temperature of such air flow for interrupting the current supply of the heating element.

When air is continuously circulating through the air passage heated by the heating elements located in this passage, during the normal operation of the electric sauna unit according to the invention no air just heated will pass through the opening provided above in the wall of the air passage. However, relatively cool air will be drawn from the sauna space through this opening due to the injector action, air passing simultaneously into the air passage through the open lower end thereof. If the sauna unit is covered by an object interrupting or partially obstructing the outlet flow of heated air from the open upper end of the air passage the conditions will change. The air just heated in the air passage will find a way through the opening provided above in the wall of the air passage, grazing the sensing element mounted therein which will immediately be exposed to a raised temperature. Due to the heating of the sensing element the thermostatic switch will be operated to break the supply circuit of the heating elements and, thus, the heating of the sauna unit will cease. The thermostatic switch may be adjusted to be actuated at a relatively low temperature since the temperature of the sensing element in the opening is comparatively low during the normal operation of the sauna unit, making it possible to eliminate every risk for overheating of the sauna unit to such an extent that there is impending risk for a fire.

For further details of the invention reference is made to the enclosed drawing, wherein FIG. 1 is a vertical cross sectional view of a sauna unit according to the invention when covered by an object; and

PEG. 2 is an elevational view of the rear side of the sauna unit.

The sauna unit shown in the drawing is of a construction commonly known having a metal sheet casing 10 which may be double walled and forms an air passage 11 open at the top and the bottom, in which there are located tubular electric heating elements l2, e.g., one for each phase of a three-phase supply. These heating elements are mounted on a connection box and are supported thereby cables being drawn in the conventional manner to a heat control apparatus of a known type. Heating elements 12 may extend into a chamber for heat accumulating bodies, usually stones, located in air passage ill or in another manner. As far as the arrangement of the air passage and a stone chamber, if any, is concerned, the sauna unit may be of one of the well-known constructions appearing on the market such as that disclosed in British Patent Specification No. 1,075,896. The sauna unit is adapted to be mounted close to a wall of the sauna space, e.g., on the wall proper by means of brackets or similar means, one wall lid of casing ill facing the sauna wall to form the rear wall of the unit.

in the rear wall 14 which has to be spaced an adequate distance from the sauna wall for preventing overheating of this wall at normal operation of the sauna unit there is provided an opening l5 formed as a horizontally extending narrow slot in the upper half portion of the rear wall the slot being spaced a short distance from the upper end of the sauna unit. in this opening there is mounted a sensing element in which is connected by a conduit 17 with a thermostatic switch 18 located on or in connection box l3. This sensing element in which may be formed as a tubular liquid container is mounted by means of fastening members 16' on a flap 1S deflected from the rear wall into air passage 11 about the lower edge of opening 15 when forming said opening. The liquid container is connected by a capillary tube forming conduit with a bellows or other expansion member forming part of thermostatic switch 1%. At a predetermined temperature of sensing element 16 defined by adjustment members provided in thermostatic switch it the liquid in the communicating liquid system formed by sensing element 16, conduit l7 and the expansion member of thermostatic switch 18 will have expanded to a sufficient degree to actuate thermostatic switch 18 over the expansion member. A channel 20 is mounted on the rear wall of the sauna unit to form a protection for conduit 17 which is relatively damageable.

During normal operation of the sauna unit air passes into air passage ill at the open lower end thereof and the air being heated in the air passage will leave this passage at the open upper end thereof. Part of the air will be drawn into the air passage from the sauna space also through opening 15. Now, the thermostatic switch 18 is adjusted to be maintained unacted at the temperature assumed by sensing element 16 during normal operation of the sauna unit. The thermostatic switch may be normally closed and may be connected in series with heating elements 112 in the electric circuit to be opened at a predetermined temperature of sensing element 16 which is higher than that normally assumed by the sensing element such that the current through the heating elementswill be interrupted. However, thermostatic switch 18 may also beincluded in a separate control circuit for the supply circuit of the heating elements to initiate opening of a circuit breaker when closed at said higher temperature the circuit breaker interrupting the supply circuit of the heating elements.

if it is assumed that the sauna unit is covered completely or partly by means of an object such as a towel or the like or, as illustrated in the drawing, by a panel 21 the heated air will be deflected by the covering object and will leave air passage 11 not through the upper end thereof but through opening l'as is indicated by arrows 22 in FlG. 1. The hot air flow grazing sensing element 16 raises the temperature thereof considerably and due to the fact that the thermostatic switch is adjusted to react on a relatively low temperature the heating of sensing element 16 will immediately result in an interruption of the current supply to heating elements 12. Any risk for the sauna unit ever to be heated to a temperature which is so high that a covering object or the wall behind will be ignited is thus completely eliminated by this arrangement.

The arrangement described provides an overheating protection arrangement for an electric sauna unit which is as simple as effective. The disclosed embodiment may be modified within the scope of the following claims concerning the construction of the thermostatic switch and the location as well as the arrangement of opening 15 and sensing element 16 and also concerning the construction of the sensing element.

It may be added that the overheating protection arrangement will function not only when the'sauna unit is covered but also in case the air circulation through the unit should be obstructed for other reasons for example due to defective ventilation of the sauna space or if the thermostatic means normally responsible for the temperature control in the sauna space should fail and allow un unlimited temperature raise.

What I claim is:

1. An electric sauna unit comprising: a casing adapted to be mounted adjacent a wall in a sauna space and defining an air passage having a generally vertical extension and communicating with the ambient atmosphere via the open bottom and top of the casing through which air flows during normal operation, at least one electric heating element located in said air passage, a thermostatic switch for controlling the current supply to the heating element, an opening formed in an upper part of the casing and adapted so that during normal operation of the unit it allows a flow of cool air through said opening from the outside of the casing to the air passage, whereas if the air passage is obstructed the flow of heated air will leave the air passage through said opening, and a sensing element operatively connected to the thermostatic switch being located in the said opening in order to sense the temperature of the air flow passing through said opening and adapted to actuate the thermostatic switch for interrupting the current supply to the heating element when the temperature at the opening reaches a predetermined value. v

2. An electric sauna unit as claimed in claim 1, wherein the opening is provided in a wall portion of the casing adapted to face a wall of the sauna space.

3. An electric sauna unit as claimed in claim 1, wherein the thermostatic switch is located in a lower portion of the air passage.

the sensing element being mounted on said flap, 

1. An electric sauna unit comprising: a casing adapted to be mounted adjacent a wall in a sauna space and defining an air passage having a generally vertical extension and communicating with the ambient atmosphere via the open bottom and top of the casing through which air flows during normal operation, at least one electric heating element located in said air passage, a thermostatic switch for controlling the current supply to the heating element, an opening formed in an upper part of the casing and adapted so that during normal operation of the unit it allows a flow of cool air through said opening from the outside of the casing to the air passage, whereas if the air passage is obstructed the flow of heated air will leave the air passage through said opening, and a sensing element operatively connected to the thermostatic switch being located in the said opening in order to sense the temperature of the air flow passing through said opening and adapted to actuate the thermostatic switch for interrupting the current supply to the heating element when the temperature at the opening reaches a predetermined value.
 2. An electric sauna unit as claimed in claim 1, wherein the opening is provided in a wall portion of the casing adapted to face a wall of the sauna space.
 3. An electric sauna unit as claimed in claim 1, wherein the thermostatic switch is located in a lower portion of the air passage.
 4. An electric sauna unit as claimed in claim 1, wherein the casing is provided with a flap, deflected into thE air passage at the lower margin of the opening, the sensing element being mounted on said flap. 